Telephone system



July 8, 1941. v c. E. LOMAX TELEPHONE SYSTEM Filed April 1, 1959 ZQPRE25o INVENTOR. CLARENCE E. LOMAX ATTORNEY5.

Patented July 8, 1941 TELEPHONE SYSTEM Application April 1, 1939, SerialNo. 265,460

21 Claims.

The present invention relates to improved apparatus for providingdifferent classes of service to difierent groups of substations embodiedin an automatic telephone system and, more particularly, to improvedapparatus for providing, without charge, restricted telephone service tosubstations of the paystation type.

In certain cases it is desirable that provisions be made whereby certainof the substations'of an automatic telephone system are restricted tocalls to substations within certain areas or to predetermined telephonestations. For example, in the case of a system comprising a network ofexchanges in two or more closely adjacent cities or towns, it may bedesirable to provide unlimited service to certain subscribers who pay ahigh rate for service or for substations connected for metered service,at the same time restricting other subscribers who pay a lower rate, tolocal calls within the area of one of the cities. Again, it may bedesirable to arrange the system apparatus so that calls originating atpaystations may be routed to information operators, fire stations,police stations and the like without coin deposits, while all otherconnections are only successfully obtained after the correct coindeposits have been made. Various arrangements permitting services of thecharacter just mentioned have been previously developed but the usualarrangements of this type are complicated in character and are ofrestricted application.

It is an object of the present invention to provide improved telephoneapparatus of simple and economical arrangement which is positive andreliable in its operation to provide services of the character brieflyoutlined above.

It is another object of the invention to provide in conjunction with oneor more of the substations of an automatic telephone system improvedcircuits arranged to restrict efiective operation of the calling devicesof the substations to the dialing of directory numbers having not morethan a specified number of digits.

It is a further and more specific object of the invention to provideimproved apparatus of the character mentioned wherein the restrictedoperation of the calling devices provided at certain substations cf thesystem is achieved through the provision of circuit arangements forbloclnng the flow of direct current of one polarity over the linesrespectively extending to such substations.

In the illustrated embodiment of the system there is provided onesubstation which is arranged for restricted service, together with aplurality of lines including one line extending to the substation and aplurality of automatic impulse-responsive switches controllable over thelines to establish connections therebetween. In order to restrict theservices available to the above-mentioned substation, there is seriallyincluded in the line extending thereto a unidirectional conductivedevice in the form of a rectifier, which device is so poled that, byvirtue of its current blocking characteristic, it prevents currentpulses from being transmitted to all but a few of the numerical switchesembodied in the system. The device is thus arranged to preventconnections from being routed from the substation through the regularconnector switches of the system to at least a portion of thesubscribers lines. More particularly, the substation which is arrangedfor restricted service is of the paystation type and comprises means forreceiving coins or the like which includes a coin deposit channel, acoin collect channel and a coin refund channel; together with the usualtransmitter, receiver and impulsing device. There is further provided anormally incomplete low impedance path shunting the transmitter, whichpath is effective, when completed, to render the transmitter ineffectiveto transmit signal currents over the line extending to the substation.In addition, the substation apparatus includes switching means operativein response to the deposit of a coin in the coin receiving means forshort-'circuiting the unidirectional conductive device included in theline, thereby to render this device ineffective to prevent the flow ofdirect current of either polarity over the line. This switchingapparatus further functions to complete the above-mentioned path forshort-circuiting the substation transmitter. Additional key operatedswitching means is provided which, when operated, functions toshort-circuit the unidirectional conductive device and to open theabove-mentioned low impedance path shunting the transmitter. Thisadditional switching means, when operated, further functions to permit acoin deposited in the coin deposit channel of the coin receiving meansto pass into the coin collect channel. By virtue of this arrangement thedesired coin collecting operation is performed incident to thecompletion of a talking connection involving a distant substation of thecharacter requiring a coin deposit in order to route a call thereto. Asecond key operated switching device is provided for the purpose ofobtaining coin refunds when calls originating at the substation are notsuccessfully completed. This second switching device is arranged tointerrupt an established loop circuit extending to the substation andhas associated therewith a slow-acting device which functions to retardmovement thereof from the open circuit position to the closed circuitposition, thereby to prevent fraudulent use of the substation.

Further features of the invention pertain more particularly to thespecific arrangement of the substation apparatus and of the automaticswitching apparatus embodied in the system,

whereby the above-outlined and additional operating features areobtained.

The novel features believed to be charateristic of the invention are setforth with particularity in the appended claims. The invention, both asto its organization and method of operation, together with furtherobjects and advantages thereof, will best be understood by reference tothe specification taken in connection with the accompanying drawing inwhich the single figure illustrates an automatic telephone system havingembodied therein the features of the invention briefly outlined above.

Referring now to the drawing, the system there illustrated comprises aplurality of lines, three of which are indicated at lo, M and i2,extending respectively to the substations A, B and C, together withautomatic switching apparatus for setting up connections between thelines. More particularly, the automatic switching apparatus comprisesline switches l3, l4 and I5 individually terminating the lines H], H andE2 in the order named; and a plurality of first selector switches one ofwhich is indicated at It, each having access to a. group of secondselector switches one of which is indicated at ii, and to a plurality ofspecial connector switches one of which is indicated at IS. Theautomatic switching apparatus further comprises a plurality of regularconnector switches one of which is indicated at It, these switches beingarranged in groups and each having access to a plurality of thesubscribers lines of the system. Each of the first selector, secondselector and connector switches such, for example, as the switches [5,ll, i8 and I9 includes a trunk line incoming thereto over which theswitch may be seized from any one of a group of preceding switches.These trunk lines individually comprise a pair of talking conductors anda private or control conductor. Preferably, the line switches l3, l4 andI5 and the other similar switches individually terminating thesubscribers lines of the system are of the well-known non-homing rotarytype while the first selector, second selector and connector switchesare of the well-known Strowger type of which several commercialembodiments are available. Each of the connector switches of the systemis of the wellknown calling party release type. In order more clearly toexplain the operation of the system, a portion of the control equipmentembodied in each of the switches l6, 11, I8 and I9 is illustrated indetail. More particularly, the relay equipment embodied in the firstselector switch 16 includes a line relay I00 and a switching-throughrelay H0 which latter relay functions in response to operation of theswich IE to select an idle outgoing trunk line to switch the callingloop circuit through to the succeeding switch to which the idle trunkline extends. The control apparatus of the second selector switchsimilarly comprises a line relay l20 and a switching-through relay I39.If desired, each of the first and second selector switches correspondingto and including the switches i6 and il may be of the arrangementdescribed in the book entitled Telephone Theory and Practice; Automaticswitching and auxiliary equipment, page 69, written by Kempster B.Miller and published by the MoGraw-Hill Book Company in 1933. Thespecial connector switch I8 is of the capacitance bridge type and may beof the general arrangement disclosed on page '75 of the above-mentionedpublication. The control apparatus of this switch comprises a line relayI43 and a slow-acting ring cut-off and line switching relay I56. A pairof condensers MI and I42 are serially incorporated in the conductors ofthe trunk line incoming to the switch I8 for the purpose of separatingthe calling and called loop circuits extending to this switch when aconnection routed by Way thereof is fully established. The regularconnector switch [9 may be of the same general arrangement as theconnector switch 18 and has embodied therein a line relay Ill] and 9.called party answer or battery reversing relay 180.

The switching apparatus describe above is illustrated as comprising apart of the apparatus embodied in a single automatic exchange. In theevent this exchange forms a part of a larger exchange network andfacilities are to be provided whereby the various subscribers of thenetwork may call through two or more exchanges without the assistance ofan operator, the first selector switches such, for example, as theswitch It may be given access to one or more groups of outgoingrepeaters terminating trunk lines extending to the other exchanges. Insuch case, the exchange battery voltage normally impressed across thetalking conductors of the trunks extending from the bank contacts of thefirst selector switches to the outgoing repeaters may be poled tocorrespond to the polarity of the voltage normally impressed across thetalking conductors of the trunk lines incoming to the regular connectorswitches, all in the manner more fully explained subsequently, for thepurpose of preventing the substations equipped for restricted servicefrom routing calls by way of these repeaters to substations outside ofthe restricted area.

Referring now more particularly to the substation A, the apparatusprovided at this substation comprises a transmitter 20, a receiver 2!, adial operated calling or impulsing device 22 and a hook or cradle switch23 which is operative from its normal position as shown in the drawing,to its oil-normal position to complete a loop circuit including theconductors of the line If! and extending to the line switch l3. For thepurpose of blocking the flow of current of one polarity over the line iii, there is provided a unidirectional conductive device in the form ofa copper oxide rectifier 24 which is adapted to be included in the loopcircuit established by way of the line It when the hook switch 23 isoperated to its oilnormal position. This device is shunted bycapacitance means in the form of a condenser 25, thereby to provide asignal current by-pass when the device is operatively included in anestablished loop circuit including the line H]. The apparatus providedat the substation A further comprises coin receiving means whichincludes a coin deposit channel or chute 26, a coin collect channel orchute 21 and a coin refund channel or chute 28. For the purpose ofshort-circuiting the rectifier 24 when a coin is deposited in the coindeposit chute 26 of the coin receiving means, there by to condition thesubstation circuit for unlimited service, there is provided a switchingdevice 29 comprising two movable contact springs 29a and 29b and anactuating member 30 which projects within the coin deposit chute 26. Thefree ends of the movable contact springs 29a and 2% respectivelycooperate with latching elements 3 la and 3lb, both mounted near thefree end of a cantilever mounted spring 32. The movable contact spring290. in cooperation with its associated fixed contact is arranged tocomplete a low impedance path comprising a resistor 33 for shunting thetransmitter 20. This path, when completed, renders the transmitterineffective to transmit signal currents over the line H), althoughpermitting a suihcient portion of incoming signal currents to traversethe receiver 2| to cause audible reproduction thereof. In order tointerrupt this path following the completion of a desired taikingconnection, there is provided a key operated switching device 34 whichincludes four contact springs 34a, 34?), Ste and Sid, and an actuatingmember 35 which is arranged to cooperate with the latching spring 33 tomove the two latching elements em and 35b out of engagement with thesprings Eta and 2%, respectively. The actuating member 35 is alsoarranged to operate a rocker arm 36 which normally projects within thecoin collect chute 21 to prevent a coin deposited in the coin depositchute 26 from passing into the coin collect chute 2?. The key operatedswitching device 34 is of the locking type. More particular-.51, thedevice includes a latching element 3? which is normally biased intoengagement with the free end of the contact spring 352a by means of acantilever mounted biasing spring 33. This latching element is arrangedto be operated out of engagement with the spring 3 3a by means of anoperating magnet 39 which, when energized, attracts a magnetic armaturemember, not shown, carried by the spring 38. For the purpose ofpreventing coins deposited in the coin deposit channel 26 of the coinreceiving means from passing into the coin refund chute 28, there isprovided a rocker arm 46 which is arranged to be controlled by a secondkey operated switching device including an actuating member i! springre. The actuating member A! is also arranged to operate the spring 32inorder to move the latching elements em and 3th out of engagement withthe springs 29a and 2%, respectively. The movable contact spring d2 ofthe second switching device is provided for the purpose of interruptingan established loop circuit extending by way of the line i9, thereby toinitiate the release of an operated switch train,

in any case when this device is operated to obtain the refund of adeposited coin. In order to insure the release of the operated switchtrain each time a coin refund operation is performed, there isoperatively associated with the actuating member ll a slow-acting devicein the form of a dashpot 43 which functions to retard movement of themember M from its cit -normal position to its normal position.

Referring now more particularly to the operation of the system andconsidering first calls originating at the substation A, it is pointedout that such calls are initiated in the unusal manner by removing thereceiver 2! from the supporting hook of the hook switch 23. When thisoperation is performed the hook switch 23 is operated to its off-norma1position to open, at its springs 23a and 23b, a point in the circuittraced hereinafter for energizing the release magnet 39, and to completea loop circuit extending to the line switch i3. This loop circuit maypartially be traced as extending by way of the line conductor illa, thepulsing springs 22a of the impulsing device 22, the rectifier 24, theswitch spring 230 and the associated switch hook, the transmitter 25,the receiver 2i and the contact spring 132 to the opposite lineconductor we. The line switch i3 responds to completion of this loopcircuit by operating in the usual manner to mark the calling line 26 asbusy in bank contacts of the connector switches having access theretoand t select and a movable contact an idle one of the first selectorswitches to which it has access. Assuming, for example, that the firstselector switch It is the first idle one of the selector switches towhich the line switch it has access, when the trunk line extending tothis selector switch is tested and found to be idle, the line switch I3operates to switch the calling loop circuit through thereto, thereby toenergize the line relay me. In this regard, it is pointed out that theexchange battery is connected to the windings of the line relay embodiedin the line switch is and of the line relay H30 in a manner such thatcurrent flow over the established loop circuit is not blocked by therectifier 24 included therein. Foliowing the completion of this loopcircuit and when the line relay mil operates, the remaining controlapparatus of the selector switch It is conditioned to respond to thefirst operation of the impulsing device 22 provided at the substation A.

The next operation performed by the calling party using the substation Adepends upon the type of call being initiated. Thus, if the call is tobe forwarded to the telephone station B, for example, which may bereached without a coin deposit, the calling party proceeds to dial thedirectory number of this substation in the usual manner. Alternatively,if the call is to be forwarded to a substation such, for example, as thesubstation C associated with a line terminating at one of the regularconnector switches of the system, the calling party must first deposit acoin in the coin deposit chute 26 before more than one digit is dialedand preferably before the dialing operation is started. Assuming firstthat the call under consideration is to be forwarded. to the telephonesubstation B, the impulsing device 22 is operated in accordance with thedirectory number designating the called substation. During eachoperation of the calling device the pulsing springs 22a, are opened andclosed one or more times depending upon the character of the digitdialed. The line relay I68 of the first selector switch l6 follows theimpulses of the first digit and repeats these impulses to the verticalmagnet of the switch 16 in the usual manner, whereby the wipers of theswitch are elevated to a position opposite the level of bank contactsterminating the desired group of trunk lines. At the end of the digitand during the inter-digit pause between the first and second operationsof the impulsing device 22, the rotary magnet conventionally embodied inthe switch 16 functions to rotate the wipers of this switch over thebank contacts terminating the selected group of trunk lines until anidle one of these lines is selected. If, for example, the connectorswitch I8 is one of the group of connector switches selected in responseto the group selecting operation of the selector switch it and furtherthe switch I8 is the first available idle switch of the selected group,when the wipers of the selector switch it engage the contactsterminating the conductors of the trunk line extending to this connectorswitch, the switching-through relay 5 ii! is energized and operates inthe usual manner. Upon operating, the relay I It, at its armatures I i land l I 2 and their respective associated working contacts, switches thecalling loop circuit through to the selected connector switch is causingthe line relay I49 embodied in this connector switch to be energized.The line relay Hi9 now operates, it being pointed out that the exchangebattery is connected to the battery terminals of this line relay i-namanner such that the recti fier 24 does not block the flow of currentover the loop circuit. Upon operating, the relay I40 causes theoperation of the hold relay, not shown, but conventionally provided inthe connector switch I8. The hold relay, in turn, operates to impressground potential upon the private conductor of the trunk line incomingto the connector switch I8, thereby to maintain the switchingthroughrelay I II] of the preceding selector switch I6 operated and to guardthis connector switch against seizure by another of the first selectorswitch having access thereto. Following the operations just described,the connector switch I8 is conditioned to respond to the impulsestransmitted over the calling loop circuit incident to further operationof the impulsing device 22. The line relay I40 follows the impulses ofthe second digit and functions to repeat the impulses to the verticalmagnet embodied in the connector switch I8. As a result, the wipers ofthis switch are elevated, in the usual manner, to a position oppositethe level of bank contacts terminating the group of lines including theline II. Thereafter and when the third digit is dialed at the callingsubstation, impulses are delivered, through operation of the line relayI40, to the rotary magnet of the connector switch I8 so that the wipersof this switch are rotated into engagement with the set of contactsterminating the conductors of the line II. At the end of the third digitthe selected line is tested in the usual manner to determine the idle orbusy condition thereof and, if busy, busy tone current is returned overthe calling loop circuit to signal the calling party that the desiredconnection cannot be obtained. Alternatively, if the line II is idle atthe time it is selected, the control apparatus embodied in the connectorswitch I8 automatically operates to project ringing current over theline for the purpose of energizing the signal device provided at thesubstation B, and to return the usual ring-back tone signal to thecalling party. When the call is answered at the called substation, adirect current bridge is connected across the conductors of the line IIto complete a circuit including the armatures I! and I52 of the ringcut-off relay I50 for energizing the upper winding of this relay. Uponoperating, the ring cutoff relay I50 completes, at its armature I53, alocking circuit for itself and thereafter completes, at its armaturesI5I and I52 and their respective associated working contacts, thedesired communication connection between the calling and calledsubstation.

The release of the connection established in the manner just describedis entirely under the control of the calling party. More particularly,when the receiver 2| is replaced upon its supporting hook to causeoperation of the hook switch 23 from its oif-normal position to itsnormal position, the switch hook is disengaged from its asssociatedcontact 23c to interrupt the loop circuit extending from the substationA to the operated connector switch I8. As a result, the line relay I40is deenergizod and restores to initiate the release of the connectorswitch I8 in the usual manner. During the release of this connectorswitch, ground potential is removed from the control or privateconductor of the trunk line extending thereto, whereby the precedingoperated.- selector switch it is released in the usual manner. Whenground potential is removed from the private conductor of the trunk lineextending to the selector switch IS, the line switch I3 is also restoredto normal in a conventional manner. During the release of this lineswitch, ground potential is removed from the privatae conductor of thecalling line IEI so that this line is marked as idle in the bankcontacts of the connector switches having access thereto. Thus, theapparatus utilized in establishing the connection is fully released andis rendered available for further use.

From the preceding explanation with reference to the call routed to thesubstation B, it will be apparent that the calls may be successfullycompleted so long as the unidirectional conductive device 24 does notinterfere with the flow of direct current over an established callingloop circuit extending from the substation A, as this loop circuit issuccessively extended to the selector and connector switches. In thecall just described, the failure of the device 24 to block the flow ofdirect current over the calling loop circuit is due to the manner inwhich the line relays I and I40 respectively embodied in the switches I6and I3 are connected to the exchange battery. It will be apparent,therefore, that calls originating at the substation A and routed throughthe special switches corresponding to and including the con nectorswitch I8 to specified ones of the substation lines embodied in thesystem may be successfully completed without coin deposits at thecalling substation. On the other hand, if a calling party at thesubstation A attempts to obtain a connection to a substation associatedwith a line not accessible to the special connector switches, theundirectional conductive device 24 functions to block the progress ofthe call after it proceeds to a certain point. Thus, if a calling partyattempts, without making a coin deposit, to route a connection to thesubstation line I2 by dialing the directory number of the substation C,the first two digits dialed cause the connection to be routed to one ofthe regular connector switches of the system. Assuming that the switchesI6 and I! are successsfully operated in response to the first two digitsdialed at the substation A and further that the second selector switchI! operates to seize the connector switch I9 having access to the calledline I2, when the calling loop circuit is switched through to thisconnector switch the voltage oil the exchange battery is impressed uponthis loop circuit through the windings of the line relay I'iIl. Thisline relay is reversely connected to the exchange battery. Hence, thepolarity of the voltage impressed upon the calling loop circuit is suchthat the unidirectional conductive device 24 blocks the flow of currentover this circuit, and the line relay Ill! does not operate.Accordingly, the hold relay conventionally embodied in the connectorswitch I9 and controlled by the line relay I'Ii] does not operate andholding ground potential is not impressed upon the control conductor ofthe trunk line incoming to the connector switch I9. The absence ofground potential from the indicated control conductor causes thepreceding selector switches I1 and IE to be released. Since the callingloop circuit including the calling line I0 is not interrupted during therelease of the two switches I6 and H, the first-mentioned of theseswitches is reseized immediately following its release. Hence, the lasttwo digits of the directory number designating the substation C anddialed at the calling substation are absorbed by the selector switch I6and an idle second selector switch or connector switch seized by theswitch I6. Thus, the call intended for the substation C is notcompleted. The calling subscriber, upon failing to receive the usualring back tone signal, will, of

course, replace the receiver 2! upon the switch hook of the hook switch23, thereby to interrupt the calling loop circuit and to initiate therelease of the operated switch train in the previously described manner.

As previously indicated, if the dialing operation is preceded by thedeposit of a coin in the coin receiving means, the rectifier 24 isrendered ineffective to restrict the effective operation of theimpulsing device 22. Thus, in making the call just considered, if thecalling party deposits a coin in the coin deposit chute 26 followingremoval of the receiver 2| from the switch hook and prior to operationof the calling device 22, the passage of this coin through the coindeposit channel 26 causes the switch 29 to operate and short-circuit therectifier 24. More particularly, when the deposited coin engages theactuating member 35 the movable contact springs 29a and 2% are moved tothe left into engagement with their respective associated fixed contactsand the free ends of these springs are moved over the latching elementsem and 3th, respectively, permitting the spring 32 to flex upwardly sothat the indicated latching elements restrain the springs 29a and 29b intheir respective operated positions. With the contact spring 2% engagingits asssociated fixed contact, an obvious path is completed forshort-circuiting the rectifier 24 and with the contact spring 29aengaging its associated fixed contact, the above-mentioned low impedancepath including the resistor 33 is completed for short-circuiting thetransmitter 22; in series with the receiver 2!. With the rectifier 2Gexcluded from the calling loo-p circuit, it will be apparent that thedirection of current flow over this circuit may be reversed at will asthe call proceeds through the automatic switching apparatus of the lineterminating exchange. Accordingly, in the case under consideration thecall may be routed through the switches it, I! and IS in succession tothe desired called line l2. When the call is answered at the calledsubstation C, a d rect current bridge is connected across the conductorsof the line 12 and the battery reversing relay lot? is caused to operatein the usual manner. This relay, upon operating, actuatesits armaturesI8| to I84, inclusive, to reverse the direction of current flow over theloop circuit extending through the switches 15 and H to the callingsubstation. Following the completion of the desired talking connectionin the manner just described, the receiver 2| responds to signalcurrents transmitted over this connection to the substation A to asufhcient extent to enable the calling party to determine that the callhas been answered, even though the low impedance shunt path comprisingthe resistor 33 prevents the major portion of the signal currents fromtraversing the windings of the receiver. The transmitter 25, on theother hand, is rendered substantially inoperative to transmit signalcurrents over the line I!) so long as this low impedance path iscompleted. In order to render the transmitter 26 operative, the callingparty, upon ascertaining that the call has been answered, depresses theactuating member 35 of the switch 34, thereby to cause the low impedancepath shunting the transmitter 2% and the receiver 2! to be interrupted.More particularly, when the member 35 is) depressed the switch springs Slb, 3G0 and 3M are first operated into engagement to complete obviouspaths for short-circuiting the rectifier 24 and the pulsing spring 2211of the impulsing device 22. During such movement of the member 35 thespring 34a is also operated into engagement with its associated fixedcontact to prepare the previously mentioned circuit for energizing therelease magnet 39. During the downward movement of the spring 34a thefree end of this spring rides over the latching element 3'! permittingthe spring 38 to flex to the left, thereby to latch the spring 34a andthe member 35 in their respective operated positions. During thedownward movement of the member 35 the free end of the cantilevermounted spring 32 is moved downward so that the latching elements 35aand M22 are carried out of engagement with the free ends of the contactsprings 29a and 29b. Accordingly, these springs are permitted to returnto their respective normal positions out of'engagement with theirrespective associated fixed contacts. Thus, the first completed path forshort-circuiting the rectifier 24 is interrupted and the above-tracedlow impedance path shunting the transmitter 20 is opened, thereby torender this transmitter operative to project signal currents over theestablished talking circuit. As the member 35 of the switch 34 isdepressed in the manner just explained, it functions to rock the arm 36in a clockwise direction so that the coin blocking finger of this arm ismoved out of the coin collect chute 21, permitting the coin deposited inthe chute 26 to pass from this chute into the coin collect chute 2! andthrough this chute into the usual coin collect box. It will be notedthat in any case when the member 35 is operated to complete the pathshort circuiting the rectifier 24, the springs 34b, 34c and 34d. aremoved into engagement to short circuit the pulsing springs 22a. Thus,the switch 34 cannot be operated to short circuit the rectifier withoutendering the impulsing device ineffective to transmit control pulsesover the line It and fraudulent use of the apparatus is prevented.

At the end of the conversation and when the connection is cleared out atthe calling substation A, the operated switching apparatus comprisingthe switches l3, It, I? and i9 is released in the conventional mannerbriefly explained above. During the release of the apparatus the switch34 is restored to normal when the receiver 2! is replaced upon theswitch hook of the hook switch 23. More particularly, when the hookswitch 23 is actuated from its off-normal position to its normalposition, the spring 23a is first moved into engagement with the spring2311 and thereafter the switch hook is moved out of engagement with thespring 23c, thereby to include the winding of the release magnet 29 inthe calling loop circuit. Specifically, this magnet is energized over acircuit which may be partially traced as extending by way of the lineconductor Hid, the switch springs 34d, 340, 3%, 23b and 2311., thewinding of the magnet 39, the spring 34a and its associated fixedcontact, the transmitter 2t, the receiver 2|, the contact spring 42 andthe opposite line conductor iiib. When energized over this circuit themagnet 39 attracts the armature carried by the latching spring 38,causing this spring to be moved to the right so that the latchingelement 31 carried thereby releases the free end of the spring 340,. Asa result, the key switch 34 is permitted to restore to its normalposition. During such restoration of the switch 34, the spring 34a ismoved out of engagement with its associated fixed contact to interruptthe calling loop circuit and thereby deenergize the winding of themagnet 39. Also during restoration of the switch 34, the spring 32 andthe rocker arm 3% are restored to their respective normal positions andthe springs 34b,

340 and 34d are moved out of engagement to open the above-describedpaths for, short-circuiting the pulsing springs 22a and the rectifier Ei. Thus, the apparatus provided at the substation A is fully restored tonormal.

If a call initiated at the substation A is not successfully completeddue to the busy condition of the called line or is abandoned before thedialing operation is completed, the operated switch train through whichthe call is routed is released in the usual manner when the receiver 2|is replaced upon the switch hook of the hook switch 23. In such case, ifa coin has been deposited in the coin deposit chute 26 of the coinreceiving means, it is held between the coin blocking fingers of the tworocker arms 36 and and the switch 23 is restrained to its off-normalposition. In order to restore the switch 29 to normal and to obtain arefund of the deposited coin, the callins party may depress the key ormember 4!. When this key is moved downward the spring 32 is moved todisengage the latching elements (Ma and 3H; from the springs 29a and291) so that the switch 29 is permitted to restore to normal. During thedownward movement of the key il the rocker arm is also rotated in acounter-clockwise direction so that the coin blocking finger thereof ismoved out of the coin refund chute 26, permitting the deposited coin topass into the refund chute 23 and by way of this chute to the coinrefund pocket conventionally embodied in substations of the paystationtype. Operation of the key 4-! further results in movement of thecontact spring 42 out of engagement with its associated fixed contact toopen a. point 4 in the previously traced loop circuit including theconductors of the line in and extending to the line switch it. Thepurpose of providing the switching elements comprising the contactspring 42, in association with the key 4|, is to prevent fraudulent useof the substation apparatus. More particularly, these switching elementsinsure the interruption of an established calling loop circuit in anycase when a coin refund is obtained. This interruption of the callingloop circuit in turn results in the release of the operated switch trainin the usual manner. It will be apparent, however, that, if theswitching elements controlled by the key M were operated out ofengagement and then back into engagement with sufficient rapidity, itmight be possible for a user of the apparatus to obtain a coin refundwithout releasing an established switch train. In order to obviate thispossibility, the member li is mechanically connected to the plunger ofthe dashpot 43, this dashpot being so arranged that movement of themember l! back to its normal position following operation thereof todisengage the spring 42 from its associated fixed contact is retarded asufficient amount to permit the complete release of an operated switchtrain before the spring 42 reengages its associated fixed contact. Theprovision of the dashpot 43, operatively associated with the member M,also prevents this member from being intermittently operated to transmitswitch control pulses over the line l6 for the purpose of securing anunauthorized connection without a coin deposit.

On a call incoming to the substation A, the signal device 9 is energizedto indicate the presence of the incoming call on the line It) whenringing current is projected over this line from the operated connectorswitch through which the call is routed. With the arrangementillustrated,

the party who answers the call may, by first removing the receiver Zlfrom the switch hook of the hook switch 23 and then depressing theactuating member 35 of the switch 34, cause the desired conversationalcircuit to be completed in the usual manner, regardless of thearrangement of the connector switch through which the call is routed.Thus, with the switch 34 operated to its off-normal position, therectifier 24 is shunted from the line so that current of either polaritymay flow over this line. Accordingly, the battery cut-off relay embodiedin the connector switch through which the call is routed is caused tooperate, regardless of the manner in which the windings of this relayare connected to the exchange battery. In order more fully to explainthis feature of the system, it may be assumed, for example, that a callis forwarded through the connector switch iii to the substation A. Whenthe call is answered at the substation A and the above-describedoperations are performed incident to the answering of the call, a directcurrent bridge excluding the rectifier 24 is established across theconductors Illa and H32) of the line it so that the ring cutoif relayI50 is energized and operated to cause the desired conversationalcircuit to be completed. It will be noted that with the windings of thisrelay connected to the exchange battery in the manner illustrated,operation of the switch 3'? is unnecessary. More specifically, thedirection of current flow over the established loop circuit is from thepositive terminal of the exchange battery by way of the armature i522,the line conductor l lb over the bridging path between this conductorand the opposite conductor lfic, the conductor ma, the armature ifii andthe upper winding of the relay to the negative terminal of the exchangebattery. Since the rectifier 24 is poled to permit current to pass overthe line I5 in this direction, operation of the ring cut off relay I50is effected even though the switch 3 5 is not operated. If, however, thecall to the substation A is routed through a connector switch having aring cut-off relay connected to the exchange battery over connectionswhich are the reverse of those shown, for the ring cut-off relay I59,the direction of current flow is from the line conductor loa to the lineconductor lilb. In such case, the rectifier 24 functions to block theflow of current, thereby to prevent operation of the ring cut-off relayembodied in the connector switch through which the call is routed.Accordingly, the desired talking circuit cannot be established withoutoperation of the switch 34. From the foregoing explanation it will beapparent that, by incorporating rectifiers in the lines extending tosubstations other than paystations, the switching apparatus serving thelines may be so arranged that calls incoming to such lines can only besuccessfully completed if they are routed through connector switcheswhich include ring cut-off relays having windings connected to theexchange battery in a predetermined manner.

Although the invention has been described primarily with reference toits use in a substation of the paystation type, it will be understoodthat the rectifier 24 may be utilized, without changing the circuitconnections disclosed, as ameans of restricting the service available toa regular substation in which it is included. Thus, by a suitablearrangement of the switching apparatus used in substations incorporatingrectifier elements arranged in the manner shown, the substations may belimited to calls to other substations located within a predeterminedarea. Furthermore, the switching apparatus may be so arranged thatinterexchange calls are prevented although all other calls arepermitted. In the latter case, the repeaters associated with theinterofiice trunk lines may include line relays having windingsconnected to the exchange battery in a manner such that when one of therepeaters is seized, the rectifier embodied in the calling subscriberssubstation apparatus functions to block the flow of direct current overthe calling line, thereby to initiate the release of the establishedswitch train through which the call is routed. In view of the foregoingdescription it is .believed that themanner in which such repeaters couldbe arranged is fully apparent without further explanation.

While there has been described what is at present considered to be thepreferred embodiment of the invention, it will be understood thatvarious modifications may be made therein and it is intended to cover inthe appended claims all such modifications as fall within the truespirit and scope of the invention.

What is claimed is':

1. In a telephone system, a substation including a transmitter, areceiver and means for receiving a coin or the like, a line extending tosaid substation, a normally incomplete low impedance path for shuntingsaid transmitter and efiective, when completed, to render saidtransmitter ineffective to transmit signal currents over said line,means comprising a unidirectional conductive device for preventing theflow of direct current of one polarity over said line, switching meansoperative in response to the deposit of a coin in said coin receivingmeans for rendering said device ineffective to prevent the flow ofdirect current of said one polarity over said line and for completingsaid path, additional switching means also operative to render saiddevice ineffective to prevent the flow of direct current of said onepolarity over said line, and means responsive to operation of saidadditional switching means for interrupting said path.

2. In a telephone system, a substation including means for receivingcoins or the like, said coin receiving means including a coin depositchannel and a coin collect channel, a line extending to said substation,means comprising a undirectional conductive device for preventing theflow of direct current of one polarityover said line, switching meansoperative in response to the deposit of a coin in said coin depositchannel for rendering said device inefiective to prevent the flow ofdirect current of said one polarity over said line, additional switchingmeans also operative to render said device ineffective to prevent theflow of direct current of said one polarity over said line, and meansresponsive to operation of said additional switching means forpermitting a coin deposited in said coin deposit channel to pass intosaid coin collect channel.

3. In a telephone system, a substation including a transmitter, areceiver and means for receiving coins or the like, said coin receivingmeans including a coin deposit channel and a coin collect channel, aline extending to said substation, a normally incomplete low impedancepath for shunting said transmitter and efiective, when completed, torender said transmitter ineffective to transmit signal currents oversaid line, means comprising a unidirectional conductive device forpreventing the flow of direct current of one polarity over said line,switching means operative in response to the deposit of a coin in saidcoin deposit channel for rendering said device ineffective to preventthe flow of'direct current of said one polarity over said line and forcompleting said path, additional switching means also operative torender said device ineffective to prevent the flow of direct current ofsaid one polarity over said line, means responsive to operation of saidadditional switching means for interrupting said path, and means alsoresponsive to operation of said switching means for permitting a coindeposited in said coin deposit channel to pass into said coin collectchannel.

4. In a telephone system, a substation including a transmitter, areceiver, means for receiving coins or the like and a hook or cradleswitch operative between a normal position and an off -normal position,a line extending to said substation, means comprising a unidirectionalconductive device for preventing the flow of direct current of onepolarity over said line, switching means operative in response to thedeposit of a coin in said coin receiving means for rendering said deviceineffective to prevent the flow of direct current of said one polarityover said line, additional switching means having a normal position andoperative to an off-normal position also to render said deviceineffective to prevent the flow of direct current of said one polarityover said line, and means responsive to operation of said hook switchfrom its ofi-normal position to its normal position for causing saidadditional switching means to be restored to its normal position.

5. In a telephone system, a substation including a transmitter, areceiver, means for receiving coins or the like'and a hook or cradleswitch operative between a normal position and an of)?- normal position,a line extending to said substation, a normally incomplete low impedancepath for shunting said transmitter and effective, when completed, torender said transmitter ineffective-to transmit signal currents oversaid line, means comprising a unidirectional conductive device forpreventing the flow of direct current of one polarity over said line,switching means operative in response to the deposit of a coin in saidcoin receiving means for rendering said device ineffective to preventthe flow of direct current of said one polarity over said line and forcompleting said path, additional switching means having a normalposition and opera tive to an ofi-normal position also to render saiddevice ineffective to prevent the flow of direct current of said onepolarity over said line, means responsive to operation of saidadditional switching means to its ofi-normal position for interruptingsaid path, and means responsive to operation of said hook switch fromits oiT-normal position to its normal position for causing saidadditional switching means to be restored to its normal position. I

6. In a telephone system, a substation including means for receivingcoins or the like, a line extending to said substation, means comprisinga unidirectional conductive device for preventing the flow of directcurrent of one polarity over said line, a switching device having anormal position and operative to an off-normal position in response tothe deposit of a coin in said coin receiving means, means controlled bysaid switching device for rendering said unidirectional conductivedevice ineffective to prevent the flow of direct current of said onepolarity over said line, additional switching means and means controlledthereby for also rendering said unidirectional conductive deviceinefiective to prevent the flow of direct current of said one polarityover said line, and means responsive to operation of said additionalswitching means for causing said switching device to be restored to itsnormal position.

7. In a telephone system, a substation including a transmitter, areceiver, means for receiving coins or the like and a hook or cradleswitch operative between a normal position and an offnormal position, aline extending to said substation, a normally incomplete low impedancepath for shunting said transmitter and effective, when completed, torender said transmitter ineffective to transmit signal currents oversaid line, means comprising a unidirectional conductive device forpreventing the flow of direct current of one polarity over said line, aswitching device having a normal position and operative in response tothe deposit of a coin in said coin receiv ing means to short-circuitsaid unidirectional conductive device and to complete said path,additional switching means having a normal position and operative to anoff-normal position to short-circuit said unidirectional conductivedevice, said switching device being operative to its normal position tointerrupt said path in response to operation of said additionalswitching means to its ofi-normal position, and means responsive tooperation of said hook switch from its off-- normal position to itsnormal position for causing said additional switching means to berestored to normal.

8. In a telephone system, a substation including means for receivingcoins or the like, a line extending to said substation, means comprisinga unidirectional conductive device for preventing the flow of directcurrent of one polarity over said line, a switching device having anormal position and operative to an off-normal position in response tothe deposit of a coin in said coin receiving means, means controlled bysaid switching device for rendering said unidirectional conductivedevice ineffective to prevent the flow of direct current of said onepolarity over said line, additional switching means and means controlledthereby for also rendering said unidirectional conductive deviceinefiective to prevent the flow of direct current of said one polartyover said line, means responsive to operation of said additionalswitching means for causing said switching device to be restored to itsnormal position, and a second switching device operative to interrupt aloop circuit established by way of said line, said first-named switchingdevice being operative from its off-normal position to its normalposition in response to operation of said second switching device.

9. In a telephone system, a substation including a transmitter, areceiver, means for receiving coins or the like and a hook or cradleswitch operative between a normal position and an offnormal position, aline extending to said substation, a normally incomplete low impedancepath for shunting said transmitter and effective, when completed, torender said transmitter ineffcctive to transmit signal currents oversaid line, means comprising a unidirectional conductive device forpreventing the flow of direct current of one polarity over said line, aswitching device having a normal position and operative in response tothe deposit of a coin in said coin receiving means to short-circuit saidunidirectional conductive device and to complete said path, additionalswitching means having a normal position and opera-tive to an cit-normalposition to short-circuit said unidirectional conductive device, saidswitching device being operative to its normal position to interruptsaid path in response to operation of said additional switching means toits chi-normal position, means responsive to operation of said hookswitch from its ofi-normal position to its normal position for causingsaid additional switching means to be restored to normal, and a secondswitching device operative to interrupt a loop circuit established byway of said line, said first-named switching device being operative fromits off-normal position to its normal position in response to operationof said second switching device.

10. In a telephone system, a substation including a hook or cradleswitch and means {or receiving coins or the like, said coin receivingmeans including a coin deposit channel and a coin refund channel, a lineextending to said substation, means including said hook switch forestablishing a loop circuit including said line, additional switchingmeans having a first position and operative to a second position tointerrupt said loop circuit, means controlled by said additionalswitching means for permitting a coin deposited in said coin depositchannel to pass into said refund channel, and a slow-acting device forretarding movement of said switching means from said second position tosaid first position.

11. In a telephone system, a substation including a transmitter, areceiver and means for receiving a coin or the like, a line extendingto-said substation, a normally incomplete low impedance path forshunting said transmitter and effective, when completed, to render saidtransmitter in effective to transmit signal currents over said line,means comprising a unidirectional conductive device serially included insaid line for preventing the flow of direct current over said line,capacitance means shunting said device to provide a bypass for signalcurrents, switching means operative in response to the deposit of a coinin said coin receiving means to short-circuit said device and completesaid path, additional switching means also operative to short-circuitsaid device, and means responsive to operation of said additio nalswitching means for interrupting said path.

12. In a telephone system, a substation including a hook or cradleswitch and means for receiving coins or the like, said coin receivingmeans including a coin deposit channel and a coin refund channel, a lineextending to said substation, a plurality of impulse responsive callforwarding switches controllable over a loop circuit including said lineand successively operative in response to successive operations of saidimpulsing device, means including said hook switch for completing saidloop circuit, circuit means for preventing said switches from respondingto more than a predetermined number of operations of said device, meansresponsive to the deposit of a coin in said coin deposit channel forrendering said circuit means inefiective to restrict the effectiveoperation of said impulsing device, additional switching means having afirst position and operative to a second position to interrupt said loopcircuit, means controlled by said additional switching means forpermitting a coin deposited in said deposit channel to pass into saidcoin refund channel, means also controlled by said additional switchingmeans for conditioning said circuit means to restrict effectiveoperation of said impulsing device, and a slow-acting device forretarding movement of said additional switching means from said secondposition to said first position.

13. In a telephone system, a substation, a plurality of lines includingone line extending to said substation, a plurality of automatic switchescontrollable over said lines to establish connections between saidlines, a unidirectional conductive device adapted to be included in acalling circuit established by way of said one line, and means includingsaid unidirectional conductive device for preventing calls originatingat said substation from being routed through certain of said switches.

14. In a telephone system, a plurality of lines, a plurality ofautomatic impulse-responsive switches controllable over said lines toestablish connections between said lines, a substation including animpulsing device operative to transmit impulses over one of said lines,a unidirectional conductive device adapted to be included in a callingcircuit established by way of said one line, and means including saidunidirectional conductive device for preventing more than apredetermined number of impulse digits, resulting from operation of saidimpulsing device, from efiecting operation of said switches to establisha connection.

15. In a telephone system, a substation, a plurality of lines includingone line extending to said substation, a plurality of automatic switchescontrollable over calling circuits including said lines to establishconnection between said lines, each of a first group of said switchesbeing so connected and arranged that, when seized, current of onepolarity is returned over the calling circuit extending thereto, each ofa second group of said switches being so connected and arranged that,when seized, current of the opposite polarity is returned over thecalling circuit extending thereto, a unidirectional conductive deviceadapted to be included in a calling circuit established by way of saidone line, and means including said unidirectional conductive device forpreventing current of said one polarity from flowing over said one line,thereby to prevent connections from being routed from said substationthrough the switches of said first group.

16. In a telephone system, a substation, a plurality of lines includingone line extending to said substation, a plurality of automatic switchescontrollable over loop circuits including said lines to establishconnections between said lines, each of a first group orf said switchesbeing so connected and arranged that, when seized, current of onepolarity is returned over the calling loop circuit extending thereto,each of a second group of said switches being so connected and arrangedthat, when seized, current of the opposite polarity is returned over thecalling loop circuit extending thereto, a unidirectional conductivedevice serially connected in said one line and adapted to be included ina loop circuit established by way of said one line, and means includingsaid unidirectional conductive device for preventing current of said onepolarity from flowing over said one line, thereby to cause the releaseof a switch train through which a connection is routed from said oneline to any one of the switches of said first group.

17. In a telephone system, a substation including means for receivingcoins or the like, a plurality of lines including one line extending tosaid substation, a plurality of automatic switches controllable oversaid lines to establish connections between said lines, a unidirectionalconductive device adapted to be included in a calling circuitestablished by way of said one line, means including said device forpreventing calls originating at said substation from being routedthrough certain of said switches, and means responsive to the deposit ofa coin in said coin receiving means for rendering said deviceinefiective to prevent calls originating at said substation from beingrouted through said last-named switches.

18. In a telephone system, a plurality of lines, a plurality ofautomatic impulse-responsive switches controllable over said lines toestablish connections between said lines, a substation including meansfor receiving coins or the like and an impulsing device operative totransmit impulses over one of said lines, a unidirectional conductivedevice adapted to be included in a calling circuit established by way ofsaid one line, means including said unidirectional conductive device forpreventing more than a predetermined number of impulse digits, resultingfrom operation of said impulsing device, from efiecting operation ofsaid switches to establish a connection, and means responsive to thedeposit of a coin in said coin receiving means for rendering saidunidirectional conductive device ineffective to restrict the effectiveoperation of said imp-ulsing device.

19. In a telephone system, a substation including means for receivingcoins or the like, a plurality of lines including one line extending tosaid substation, a plurality of automatic switches controllable overloop circuits including said lines to establish connections between saidlines, each of a first group of said switches being so connected andarranged that, when seized, current of one polarity is returned over thecalling loop circuit extending thereto, each of a second group of saidswitches being so connected and arranged that, when seized, current ofthe opposite polarity is returned over the calling loop circuitextending thereto, a unidirectional conductive device adapted to beincluded in a loop circuit established by way of said one line, meansincluding said unidirectional conductive device for preventing currentof said one polarity from flowing over said one line, thereby to preventconnections from being routed from said substation through the switchesof said first group, and means responsive to the deposit of a coin insaid coin receiving means for rendering said device ineffective toprevent current of said one polarity from flowing over said one line.

20. In a telephone system, a substation, a line extending to saidsubstation, a plurality of automatic switches having access to said lineand operative to route connections to said line, and means comprising aunidirectional conductive device serially included in said line forpreventing certain of said switches from operating to completeconnections including said line.

21. In a telephone system, a substation, a line extending to saidsubstation, a plurality of automatic switches having access to said lineand operative to route connections to said line, means comprising aunidirectional conductive device serially included in said line forpreventing certain of said switches from operating to completeconnections including said line, and switching means at said substationfor short-circuiting said device, thereby to render said last-namedswitches operative to complete connections including said line.

CLARENCE E. LOMAX.

